Deformation transients of confined droplets within interacting electric and magnetic field environment

TL;DR

This paper develops an analytical model for the deformation dynamics of confined liquid droplets under combined electric and magnetic fields, revealing exponential deformation behavior and the influence of field interactions.

Contribution

It introduces a novel analytical solution for electro-magneto-hydrodynamics of leaky dielectric droplets, including a magnetic discriminating function and deformation analysis under combined fields.

Findings

Deformation follows exponential temporal evolution.

Magnetic field direction influences deformation either aiding or opposing electric forces.

Low magnetic fields significantly enhance droplet deformation and internal circulation.

Abstract

A theoretical exploration and an analytical model for the electro-magneto-hydrodynamics (EMHD) of leaky dielectric liquid droplets, suspended in an immiscible confined fluid domain has been presented. The analytical solution for the system, under small deformation approximation, in creeping flow regime, has been put forward. Study of the droplet deformation suggests that its temporal evolution is exponential, and dependents on the electric and magnetic field interaction. Further, the direction of the applied magnetic field with respect to the electric field decides whether the contribution of magnetic forces opposes or aids the interfacial net electrical force due to the electric field. Validation of the proposed model at the asymptotic limits of vanishing magnetic field show that the model accurately reduces to the case of transient electrohydrodynamic model. We also propose a magnetic discriminating function to quantify the steady-state droplet deformation in the presence of interacting electric and magnetic fields. The change of droplets from spherical shape to prolate, and oblate spheroids, correspond to magnetic discriminating function >0 and <0 regimes, respectively. It is shown that with the aid of low magnitude magnetic field, a substantial augmentation in the deformation parameter, and the associated EMHD circulation within and around the droplet is achieved. The analysis also reveals the deformation lag and specific critical parameters that aid or suppressed this lag behaviour; discussed in terms of relevant non-dimensional parameters.